After a one-month visit, the SpaceX cargo ship was set loose Sunday morning for return to Earth. The astronauts released it using the International Space Station’s big robot arm.

The Dragon capsule is bringing back 3,500 pounds of science experiments and old equipment. The California-based SpaceX company is aiming for a Pacific splashdown in midafternoon, Eastern Daylight Time. It’s the only supply ship capable of safely returning items.

NASA is paying SpaceX and Virginia-based Orbital Sciences Corp. to make station deliveries. SpaceX is also competing for the right to ferry station astronauts, perhaps as early as 2017.

The Dragon rocketed to the space station on April 18 with a full load and arrived at the orbiting lab two days later, on Easter.